P150D
P150D-COLD START ROUGH IDLE - OPEN THROTTLE START
Theory of Operation
The objective of the Dynamic Crankshaft Fuel Control (DCFC) is to reduce the fuel as much as possible during a cold start. The DCFC begins subtracting fuel from a high limit upon a cold start and keeps removing fuel in an attempt to get to a calibrated lean limit. DCFC stops removing fuel when rough idle is detected or the lean limit is reached.
- When Monitored:
Cold start condition. Ambient Air temperature between -7° C and 50° C (19.4° F and 122° F). Engine Coolant temperature between -7° C and 50° C (19.4° F and 122° F). The difference between the Ambient Air temp and ECT temp at Start is equal to or less than 10° C (50° F). Engine running at idle only.
- Set Condition:
If a rough idle is detected, the accelerator pedal was depressed during cranking and the Dynamic Crankshaft Fuel Control remains or returns to the high limit window for a calibrated time. Two trip fault.
Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. Pre-Diagnostic Troubleshooting Procedure.
1. DTC IS ACTIVE
NOTE: Review the vehicle repair history for any misfire condition repairs that have been performed.
NOTE: Diagnose and repair any other active component or circuit DTCs before continuing with this procedure.
NOTE: Allow the engine to cool to ambient temperature before proceeding.
NOTE: Diagnose and repair any misfire DTCs before continuing with this procedure.
1. Turn the ignition on.
2. With the scan tool, select View DTCs. Copy DTC and Freeze Frame information.
3. Start the engine and allow it to reach operating temperature.
WARNING: When the engine is operating, do not stand in direct line with the fan. Do not put your hands near the pulleys, belts or fan. Do not wear loose clothing. Failure to follow these instructions may result in possible serious or fatal injury.
NOTE: Attempt to operate the vehicle under conditions similar to which the DTC was set.
4. With the scan tool, select View DTCs.
Is the DTC Active at this time?
Yes
- Go To 2
No
- Perform the INTERMITTENT CONDITION diagnostic procedure. Intermittent Condition Test.
2. VISUAL INSPECTION
NOTE: Anything that affects the speed of the crankshaft can cause this DTC to set.
Inspect the engine for any of the following conditions:
- Worn serpentine belt
- Misalignment or binding water pump, P/S pump or A/C compressor pulleys
- Improper CKP, CMP, MAP or TP Sensor mounting.
- Poor connector/terminal to component connection for CKP sensor, CMP sensor, MAP sensor, TP sensor, fuel injector, ignition coil, etc.
- Corroded PCM power or ground circuits.
- Vacuum leaks.
- Restriction in the air induction or exhaust system.
- Internal engine component malfunction.
NOTE: Rough Idle may occur and may not be caused by component failure. Any of the following conditions can be the cause:
- Moisture on ignition system components
- Insufficient fuel
- Low quality fuel
- Manual transmission bog
- Towing overload
Were any problems found?
Yes
- Repair as necessary.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.
No
- Go To 3
3. ECT SENSOR OPERATION
NOTE: For this test to be valid, the thermostat must be operating correctly.
NOTE: This test works best if performed on a cold engine (cold soak)
1. Ignition on, engine not running.
2. With a scan tool, read the Engine Coolant Temperature (ECT) Sensor value. If the engine was allowed to sit overnight (cold soak), the temperature value should be a sensible value that is somewhere close to the ambient temperature.
NOTE: If engine coolant temperature is above 82° C (180° F), allow the engine to cool until 65° C (150° F) is reached.
3. Start the Engine.
4. During engine warm-up, monitor the ECT Sensor value. The temperature value change should be a smooth transition from start up to normal operating temperature 82° C (180° F). The value should reach at least 82° C (180° F).
Did the ECT value increase smoothly and did it reach at least 182° C (180° F)?
Yes
- Go To 4
No
- Verify that there is good pin to terminal contact in the ECT Sensor and Powertrain Control Module connectors. Replace the ECT Sensor if no problems were found with the connectors.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.
4. MAP SENSOR OPERATION
1. Ignition on, engine not running.
2. With a scan tool, read the Barometric Pressure.
NOTE: The Barometric Pressure should be approximately equal to the actual barometric pressure.
3. Turn the ignition off.
4. Connect a Vacuum Gauge to a Manifold Vacuum source.
WARNING: When the engine is operating, do not stand in direct line with the fan. Do not put your hands near the pulleys, belts or fan. Do not wear loose clothing. Failure to follow these instructions may result in possible serious or fatal injury.
5. Start the engine.
6. Allow the engine to idle.
NOTE: If engine will not idle, maintain a constant RPM above idle.
7. Using the scan tool, read the MAP Sensor vacuum value.
NOTE: If necessary, compare the Barometric Pressure value of this vehicle to the value of a known good vehicle of a similar make and model.
Is the scan tool reading for MAP Vacuum within 1 inch of Hg on the Vacuum Gauge and is the Barometric Pressure reading of the vehicle the approximately the same as actual Barometric Pressure?
Yes
- Go To 5
No
- Verify that there is good pin to terminal contact in the MAP Sensor and Powertrain Control Module connectors. Replace the MAP Sensor if no problems were found with the connectors.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.
5. CHECKING THE FUEL DELIVERY SYSTEM
1. Checking the Fuel Delivery System Perform the diagnostic procedure for Checking the Fuel Delivery System.
Were any problems found?
Yes
- Repair as necessary.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.
No
- Go To 6
6. CHECKING THE OXYGEN SENSOR OPERATION
1. Checking the Oxygen Sensor Operation Perform the diagnostic procedure for Checking the Oxygen Sensor Operation.
Were any problems found?
Yes
- Repair as necessary.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.
No
- Go To 7
7. IGNITION SYSTEM OPERATION
WARNING: When the engine is operating, do not stand in direct line with the fan. Do not put your hands near the pulleys, belts or fan. Do not wear loose clothing. Failure to follow these instructions may result in possible serious or fatal injury.
1. Turn the ignition off.
2. Remove the Ignition wire/coil from the Spark Plug.
3. Disconnect Fuel Injector harness connector of the cylinder being tested.
4. Install a spark tester on the Ignition wire.
5. While cranking the engine observe the spark coming from the spark tester.
NOTE: A crisp blue spark that is able to jump the gap of the spark tester should be generated.
Is good spark present?
Yes
- Go To 8
No
- Go To 9 NOTE: Connect the Fuel Injector harness connector before continuing.
8. SPARK PLUG
1. Turn the ignition off.
2. Remove the Spark Plug.
3. Inspect the Spark Plug for the following conditions:
- Cracks
- Carbon Tracking
- Foreign Material
- Gap size out of specifications
- Loose or broken electrode
NOTE: Lightly tap the bottom of the spark plug on a solid surface. The electrode in the spark plug should not move.
Were any of the above conditions present?
Yes
- Replace the Spark Plug.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.
No
- Go To 11
9. IGNITION WIRE
NOTE: If the vehicle or the cylinder being tested does not have an ignition wire answer YES to this test and continue.
1. Turn the ignition off.
2. Remove the ignition wire.
3. Measure the resistance of the ignition wire.
Is the resistance below 10K Ohms?
Yes
- Go To 10
No
- Replace the Ignition Wire.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.
10. IGNITION COIL
WARNING: When the engine is operating, do not stand in direct line with the fan. Do not put your hands near the pulleys, belts or fan. Do not wear loose clothing. Failure to follow these instructions may result in possible serious or fatal injury.
NOTE: The 3.7L V6 engine uses a modified Distributorless Ignition System (DIS) with coil consolidation on the left side engine bank.
1. Disconnect the Ignition Coil harness connector.
2. Using a 12-volt test light connected to 12-volts, probe the Coil Control circuit.
NOTE: Make sure the test light is probing the circuit before actuating the Coil or a DTC may set and not allow the actuation.
3. Crank the engine for five seconds while observing the test light.
Does the test light brightly blink/flicker while the engine was cranking?
Yes
- Verify that there is good pin to terminal contact in the related Injector and the Powertrain Control Module connectors. If OK, replace the Ignition Coil.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.
No
- Repair the excessive resistance or short in the Ignition Coil Control circuit.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.
11. ENGINE MECHANICAL
Check for any of the following conditions/mechanical problems:
- ENGINE VACUUM - must be at least 13 inches in neutral
- ENGINE VALVE TIMING - must be within specifications
- ENGINE COMPRESSION - must be within specifications
- ENGINE EXHAUST SYSTEM - must be free of any restrictions or leaks.
- ENGINE PCV SYSTEM - must flow freely
- TORQUE CONVERTER STALL SPEED - must be within specifications
- POWER BRAKE BOOSTER - no internal vacuum leaks
- FUEL - must be free of contamination
- CAM LOBES - must not be worn excessively
- CYLINDER LEAKAGE TEST - must be within specifications
- VALVE SPRINGS - cannot be weak or broken
Are there any engine mechanical problems?
Yes
- Repair as necessary.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.
No
- Go To 12
12. POWERTRAIN CONTROL MODULE (PCM)
1. Using the wiring diagram/schematic as a guide, inspect the wiring and connectors between the related Sensor, Coil, Injector and the Powertrain Control Module (PCM).
2. Look for any chafed, pierced, pinched or partially broken wires.
3. Look for broken, bent, pushed out or corroded terminals. Verify that there is good pin to terminal contact in the related Sensors, Coils, Injectors and the Powertrain Control Module connectors.
4. Perform any Technical Service Bulletins that may apply.
Were there any problems found?
Yes
- Repair as necessary.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.
No
- Replace and program the Powertrain Control Module.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.